🔍 Key Concepts

• Translational effect of twin screws when rudders are amidships • Which way a vessel moves when one propeller is still turning ahead and the other is stopped • Difference between bow movement and stern movement when one screw provides thrust and the other does not

💭 Think About

• Picture the forces: With both screws ahead and rudders amidships, what is the initial movement of the ship? Now remove the thrust from only the starboard side—what side still has forward push? • Is the active (still turning) screw on the port or starboard side? If only that side pushes ahead, which end of the vessel (bow or stern) will swing and in what direction? • Think of the ship as a lever: one side pushing ahead, the other side not. Around which point will the ship pivot, and which direction will the bow move?

✅ Before You Answer

• Identify which screw is still going ahead and which one is stopped, then note that the active screw creates forward thrust on only one side. • Separate in your mind bow motion vs stern motion—don’t confuse which end moves which way when a sideways turning moment is created. • Assume no transverse thrust effects here—focus just on the uneven ahead thrust on port vs starboard. Decide how that unbalanced thrust will turn the vessel.